1. Field of the Invention
The present invention relates to a method for noninvasive glucose sensing and a system for implementing the method and to methods for noninvasive glucose sensing with wearable devices and systems for implementing the methods.
More particularly, the present invention relates to a method for noninvasive glucose sensing including the step of measuring a thickness of a target tissue or a time of flight of ultrasound or optical pulses in the target tissue and determining a glucose value from the thickness of the target tissue or the time of flight in the target tissue in accordance with a target tissue thickness or time of flight versus glucose calibration curve and a system for implementing the method. The present invention also relates to a method for noninvasive glucose sensing using a wearable device and including the step of measuring a thickness of a target tissue or a time of flight of ultrasound or optical pulses in the target tissue and determining a glucose value from the thickness of the target tissue or the time of flight in the target tissue in accordance with a target tissue thickness or time of flight versus glucose calibration value or glucose calibration curve and a system for implementing the method.
2. Description of the Related Art
Other techniques can be used for tissue dimension measurement. Near infrared absorption spectroscopy can provide tissue thickness measurement (U.S. Pat. No. 6,671,542). However, techniques with higher resolution are needed for accurate glucose monitoring. One can use optical refractometry (U.S. Pat. No. 6,442,410) for noninvasive blood glucose measurement. However, this technique has limitations associated with low accuracy and specificity of glucose monitoring.
Other systems based on other techniques can be potentially wearable and can be used for tissue dimension measurement. Near infrared absorption spectroscopy can provide tissue thickness measurement (U.S. Pat. No. 6,671,542). However, techniques with higher resolution are needed for accurate glucose monitoring. One can use optical refractometry (U.S. Pat. No. 6,442,410) for noninvasive blood glucose measurement. However, this technique has limitations associated with low accuracy and specificity of glucose monitoring.
U.S. Pat. No. 7,039,446 B2 discloses a variety of techniques for analyte measurements but does not disclose how to measure tissue thickness and use the thickness measurements for glucose concentration monitoring. Acoustic velocity measurement in blood was proposed in U.S. Pat. No. 5,119,819 for glucose monitoring. However, tissue thickness measurements were not disclosed. Photoacoustic techniques were proposed in U.S. Pat. No. 6,846,288 B2 for measurement of blood glucose concentration by generating photoacoustic waves in blood vessels.
Most of the approaches proposed for noninvasive glucose monitoring are based on near infrared spectroscopy, Raman spectroscopy, polarimetry, and electro-impedance technique. Low glucose-induced signal and insufficient specificity and accuracy are major limitations of these approaches. Development of a noninvasive glucose monitor remains one of the most challenging (and important) biomedical problems.
These and other techniques proposed for noninvasive glucose monitoring have limited accuracy and specificity. These and other systems proposed for noninvasive glucose monitoring have limited accuracy and specificity. Moreover, the systems based on these techniques are bulky, heavy, expensive, and impractical for use as wearable devices.
Thus, there is still a need in the art for simple noninvasive glucose sensing methods and systems. Thus, there is still a need in the art for noninvasive glucose sensing methods and systems that are wearable, have acceptable size, weight, price, and are practical for use.